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04-12-2012, 01:22 PM   #1
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M 50/1.7 vs. A 50/1.7

I was wondering if the optics were similar--or identical--between the Pentax-M 50/1.7 and the Pentax-A 50/1.7.

I just recently acquired a Pentax-M 50/1.7 which I am quite fond of--I like it better than my Pentax-M 50/1.4 and perhaps better than my Pentax K 55/1.8.

I'd like this same lens with auto-aperture.

Is there a way to convert this lens to auto aperture? I don't mind losing the functionality of the aperture ring since they are inexpensive and I could get two. I got this gem for $20 (including ME super body) at the local swap meet.

04-12-2012, 01:34 PM   #2
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They changed the optics a bit in the A 50mm, and it gets slightly worse reviews, but you probably won't be able to tell a difference. You definitely won't be able to convert it to auto aperture without spending as much as the A version would cost.

50mm F1.7 Lenses - Pentax Lens Reviews & Lens Database

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04-12-2012, 01:52 PM   #3
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According to Bojidar Dimitrov, all the 50/1.7 version share the same 6 element 5 group design. I'm not sure if that 100% true though.
I did test an M version against an F version, and to my eye they performed identically.
04-12-2012, 02:35 PM   #4
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I would not bother the A50/1.7 as it is so poorly made. If you can live w/o A, the M is a joy to use.

04-12-2012, 03:05 PM   #5
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QuoteOriginally posted by wlachan Quote
as it is so poorly made.
They did drop the ball with the plastic aperture ring, but the good news is that it is a... A lens, so you can leave it in the A position.
04-12-2012, 04:28 PM   #6
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I have both and to my amatuer eyes the M is slightly sharper but the conveinience of the A is hard to beat. The A is always in the bag (usually on my K-x), the M is in the closet for when I have time and a subject that will benefit from the tack sharp lens. Either lens is a superb value in my opinion, I won't sell either. Ever. Plus I have plans to reverse the M on the front of my Sigma 105 Macro as soon as the ring gets here. As I type this I doubt I could tell you which of my pics were M or A... On that note though the A is nice for me for another reason too, the f stop data in the EXIF...


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